This invention relates to a wick operating structure of the lever actuation type for an oil burner, and more particularly to a wick operating structure for an oil burner which is adapted to vertically move a wick for the combustion and fire-extinguishing by means of an operation lever.
Recently, a wick operating structure of the lever actuation type has been widely used for an oil burner of the wick ignition type in place of a wick operating structure of the dial actuation type, because it permits a wick to be vertically moved by a simple or one-tough operation although an angle by which a wick operating shaft actuated by an operation lever is rotated is set within a small range, so that it is required to manufacture its parts with high precision. A typical wick operating structure of this type which has been conventionally used is disclosed in U.S. Pat. No. 4,726,762 issued to Nakamura et al on Feb. 23, 1988 and assigned to the assignee.
In the conventional wick operating structure which is adapted to vertically move a wick by a one-touch operation as described above is so constructed that the movement of the operation lever by a small distance causes the wick to be vertically moved in a large amount, resulting in even the movement of the lever in a small amount leading to a substantial variation in combustion. Thus, the conventional structure fails to finely adjust the combustion operation. Fortunately, this does not substantially cause a significant problem in a combustion cylinder construction employed in an old-fashioned oil burner of the wick ignition type because it is not constructed so as to carry out the adjustment of the combustion. However, it has been widely recognized in the art that this causes an important problem in an up-to-date combustion cylinder construction which is constructed so as to permit the combustion to be adjusted as desired and which has been extensively substituted for the above-described combustion cylinder construction.
Also, the conventional wick operating structure of the lever actuation type is simplified in mechanism and lightly actuated as compared with the dial-actuation-type structure, because the former merely requires to move the operation lever in a vertical direction which is a direction of movement of a wick in contrast with the fact that the latter requires a complicated mechanism for converting the rotation of a dial into the linear movement of a wick. Unfortunately, the simplification and light actuation of the structure often cause the vertical position of the wick to be readily varied due to vibration or shock applied thereto, leading to danger such as abnormal combustion or the like.
In general, a wick used in a conventional oil is covered at a tip end thereof with tar or the like and/or deteriorated by heat. Also, the wick fails to satisfactorily suck up fuel oil due to sucking-up of contaminants such as water contained in the fuel oil and the like. Thus, the wick fails to satisfactorily exhibit its function of vaporizing fuel oil at a level or vertical position predetermined for the desired combustion, leading to a decrease in combustion, so that the vertical position of the wick predetermined for the minimum combustion results in abnormal combustion which produces soot and incomplete combustion gas.
Accordingly, when a wick is deteriorated, it is required to replace the deteriorated wick with a fresh wick or vary the vertical position of the deteriorated wick depending on a degree of the deterioration to ensure the desired combustion. However, this is highly troublesome in the wick operating structure of the lever actuation type, as compared with that of the dial actuation type wherein the vertical position of a deteriorated wick is adjusted from the outside of an oil burner without disassembling the oil burner as disclosed in Japanese Utility Model Publication No. 33369/1986, which was put to practice by the assignee.
More particularly, a system employed in the structure of the dial actuation type is not applied to the structure of the lever actuation type because the wick operating structure of the lever actuation type lacks a gear mechanism as employed in that of the dial actuation type. Also, the structure of the lever actuation type, as described above, has a disadvantage that an angle at which the wick operating shaft actuated by the operation lever is rotated is set within a small range. Thus, in the wick operating structure of the operation lever actuation type, it is substantially impossible to vary or adjust the vertical position or height of the wick from the exterior of the oil burner.
Further, a conventional oil burner which employs the wick operating structure of the lever actuation type described above generally includes an automatic fire-extinguishing device. The device includes a drive plate to which a return spring is connected and which is operatively connected to the operation lever and is provided with a retaining portion normally engaged with a stopper operatively connected to a vibration sensing weight to keep the drive plate stationary. In the so-constructed automatic fire-extinguishing device, the retaining portion is released from the stopper when the vibration sensing weight falls down or tilts due to vibration or shock applied thereto and then the return spring actuates the drive plate to move the wick operating shaft to the fire-extinguishing position through the operation lever. The vibration sensing weight falling down due to vibration can right itself immediately, when it has a low center of gravity. However, when the vibration sensing weight has a high center of gravity, it is held tilted, resulting in a reset lever manually operated for resetting the vibration sensing weight being required as disclosed in Japanese Utility Model Publication No. 26701/1980. Alternatively, such a reset lever may be automatically actuated by the wick operating shaft at the fire-extinguishing position to reset the vibration sensing weight as suggested in Japanese Utility Model Application Laying-Open Publication No. 34124/1980.
In the vibration sensing weight of which a center of gravity is defined at a low level to cause the weight to right itself, it is required to reduce an angle by which the vibration sensing weight is pivotally moved. Unfortunately, this reduces a distance of movement of an actuation plate of the vibration sensing weight which functions to push up the stopper when the weight falls down, to a degree sufficient to cause malfunction of the automatic fire-extinguishing device. On the contrary, the vibration sensing weight adapted to be kept at a fallingdown state when it falls down causes a distance by which the actuation plate is moved to be substantially increased. Although this ensures the positive operation of the automatic fire-extinguishing device, it is required to arrange the reset lever for resetting the weight, resulting in the handling of the oil burner being troublesome and the construction of the oil burner being highly complicated. In addition, in the device disclosed in Japanese Utility Model Application Laying-Open Publication No. 34124/1980, the wick operating shaft is provided with a projection at a position suitable for being operatively connected to the reset lever, resulting in the reset lever being operated at the fire-extinguishing position. Such construction improves the operability of the reset lever, however, it often fails to operate the reset lever during the wick lowering operation in the case that the wick operating shaft is adapted to be rotated over an angle exceeding 360 degrees, resulting in a failure in the wick lowering operation. Also, when an angle of rotation of the wick operating shaft is set within a small range, the construction not only renders the accurate movement of the reset lever to the fire-extinguishing position highly difficult but causes the misoperation of the reset lever before the wick is fully lowered to the fire-extinguishing position to lead to the resetting of the vibration sensing weight, resulting in undesired variations in fire-extinguishing time. Unfortunately, there is not found any means which is capable of solving such a problem with a simplified structure.